1. Field of the Invention
This invention relates to polyol compositions and is more particularly concerned with novel stabilized halogenated polyol blends and their utilization in the preparation of fire retardant polyurethane foams.
2. Description of the Prior Art
It is well known in the polyurethane foam art to employ polyol blends which contain additional ingredients to the polyol itself, for example, flame retardants, catalysts, blowing agents, etc., and thereby reduce the number of components or streams that need be stored, handled, or pumped into a reaction zone; for example see U.S. Pat. No. 3,378,497.
Problems of polyol blend stability arise when the blend contains components which tend to degrade on standing, particularly, by way of the formation of minor amounts of an acidic product. Generally speaking, when the polyol blend also contains a polyurethane catalyst and acidic by-products are slowly generated in the blend, the catalyst is at least partially neutralized by the acid products and the polyol blend therefore has reduced reactivity when it is eventually reacted with an isocyanate component to form a polyurethane.
The prior art discloses means for avoiding this problem in certain cases; see for example U.S. Pat. No. 3,378,497 wherein polyol blends, which contain fire retardant organic phosphorus compounds along with organotin urethane catalysts and optionally a tertiary amine catalyst, are stabilized by the addition of a vicinal epoxide to stabilize the mixture against loss of reactivity.
U.S. Pat. No. 3,448,046 discloses polyol blends which contain chlorinated fire retardants and a minor amount of an epoxide as stabilizer.
U.S. Pat. No. 3,980,579 demonstrates that a blend of a halogenated polyol with a tertiary alkyl amine catalyst can be stabilized by including a sulfur containing organotin compound.
It has now been discovered that aliphatic polyols, rich in halogen content, when combined with a tertiary amine urethane catalyst and a minor amount of an epoxide compound selected from a particular class of epoxides, form stabilized polyol blends. The blends are stable both in respect of catalyzed polyol reactivity and blend viscosity. Amines are known curatives for epoxides but surprisingly in the polyol blends of the present invention, the amines are neither lost by reaction with the epoxide nor by neutralization by the acidic degradation products arising from the halogenated polyol. Unexpectedly, the acidic products appear to be neutralized exclusively by the epoxide.
In contrast to the prior art which stabilizes halogenated polyol blends through the use of expensive sulfur containing organotin compounds (see U.S. Pat. No. 3,980,579), the blends of the present invention achieve their stability through the use of readily available and inexpensive epoxides which, additionally, are fully reacted into the final polyurethane system. Contrastingly, the organotin mercaptides of the prior art remain as unreacted additives in the polyurethane foam.